CARBOHYDRATE FERMENTATION BY 3 SPECIES OF POLYCENTRIC RUMINAL FUNGI FROM CATTLE AND WATER-BUFFALO IN TROPICAL AUSTRALIA

Fructose, glucose and xylose were the only monosaccharides to be ferme nted by the polycentric fungi, Orpinomyces joyonii (three cattle isola tes) and O. intercalaris (two cattle isolates) and Anaeromyces spp. (f our cattle isolates and two water buffalo isolates). Both Orpinomyces spp. utilised a similar range of oligosaccharides and polysaccharides by fermenting cellobiose, gentiobiose, lactose, maltose, sucrose, cell ulose, glycogen, starch and xylan. In contrast, there was considerable variation in carbohydrate fermentation amongst Anaeromyces spp., with only cellobiose, gentiobiose and cellulose being fermented by all str ains. Formate, acetate and ethanol were the major fermentation end-pro ducts formed from glucose by all polycentric fungi. In addition, Anaer omyces spp. produced considerable amounts of lactate, although only sm all amounts were formed by Orpinomyces spp. This difference was explai ned by the low specific activity for lactate dehydrogenase in Orpinomy ces spp. Several Anaeromyces spp. also produced malate as a significan t end-product of glucose fermentation. Fermentation of specifically-la belled [C-14]glucose molecules by polycentric fungi showed that hexose was catabolised by both polycentic and monocentric fungi via the glyc olysis pathway with end-products being derived from the following carb on atoms: lactate and malate (C1-C3; C4-C6), acetate and ethanol (C1-C 2; C5-C6), CO2 and formate (C3; C4). The results were compared to thos e obtained for monocentric and polycentric fungi isolated from tempera te climate ruminants.